\begin{tikzpicture}
    \tkzDefPoints{0/0/O}
    \tkzDefPoint(30:1.5){A}
    \tkzDefPoint(160:1.0){B}

    \tkzDrawCircle[thick](O,A)
    \tkzDrawCircle[thick](O,B)
    \tkzDrawSegments(O,A  O,B)
    \tkzDrawPoint(O)
    \tkzLabelSegment[below,yshift=-.3em](O,A){$r_1$}
    \tkzLabelSegment[below](O,B){$r_2$}
    \tkzLabelPoints[below](O)
\end{tikzpicture}

